-tetrafluoroethylene is C2F4-you can chain a bunch of them together to get Teflon, -(CF2)-

-if it's not in Teflon, it's very reactive, and will react with almost anything or even just decompose into C and CF4-the reason it's reactive but Teflon is not, is because it's an unsaturated fluorocarbon -- the carbons have a double bond, instead of making more bonds to other things. Once it becomes Teflon, however, the polymerizarion means each carbon is saturated.